Two times.

First was a routine? flight back to SDF from TPA in the early 70's. First Flight was delayed by fog in TPA so I was put on a later flight that was supposed to go TPA-MCO-ATL-SDF. Got to ATL late and missed the connection. Put up in a hotel that night, 6:00A flight in the morning ATL-LEX-SDF. Well the storm that delayed the flight in TPA had frozen over all the midwest airports, but our plane left anyway. Upon landing in LEX, the runway was covered by 6 inches of ICE!. Since we were the first flight in, the runway had only had minimal clearing. Well, we hit the runway, bounced, skidded sideways and the right wing tip hit the ground throwing up a nice plume of snow. But the pilot was exceptional and got it under control and got us safely to the gate. But this was also the plane that was supposed to continue on to SDF. With a wingtip hitting the ground, they had to take it out of service. We eventually got on a later flight to SDF which was uneventful.
But watching your plane's wingtip hit the ground will get you trying to contact your Creator in a hurry!!

#2 was on our honeymoon. Flying from MIA to Puerto Plata, DR, one of the pax on the other side of the plane noticed a stream of fluid coming out of the wing. He notified the FA, who called upon the other FAs who all were looking out trying to figure it out. Meanwhile the first FA decides that the Flight Deck should be alerted, so the FO comes out to check. HE decides the Pilot needs to see it. So in the aisle between me and the right wing we now have 3 FAs, the FO, and the Pilot, as well as the three pax in the seat next to the wing. (I'm thinking. . "Who is flying the Plane? [but I knew the autopilot will fly it safely for a little while])

The pilot determines that it is either condensate from the plane being gated overnight in MIA (rained the night before) or water from the wash job they did the night before. (I was considering Hydraulic Fluid or Fuel!) But it was a rather creepy time, and I was trying to make my bride not notice the activity.